Tree physiology最新文献

Xylem properties, such as wood density and conduit diameter, are linked to crown shape and size. Suppressed trees with smaller crowns tend to have denser wood and narrower conduits at the stem base, whereas dominant trees exhibit wider conduits and lower wood density. Given the tip-to-base widening of xylem conduits-an adaptation to counteract increasing hydraulic resistance with growth-we hypothesize that hydraulic path length (i.e., the distance from leaves to the stem base) is the primary driver of conduit size, independent of cambial age. To test this, we leveraged a phenomenon in managed forests: partial harvesting reduces stand density, triggering epicormic shoot formation along the stems of uncut (standing) trees. This downward shift in leaf distribution shortens the average hydraulic path length, allowing us to assess its influence on conduit formation in the standing trees. If conduit size is governed by hydraulic path length, newly formed tree rings should contain narrower conduits following epicormic shoot sprouting, despite the older cambial age. We analysed wood samples from nine broadleaved trees across four species (Acer opalus obtusatum (Waldst. & Kit. Ex Willd.) Gams, Ostrya carpinifolia Scop., Carpinus betulus L., Sorbus aria (L.) Crantz.), comparing the median conduit area in three to four annual rings before and after the harvesting of neighbouring trees. In trees with epicormic shoots, conduit size decreased by a factor ranging from 0.93 to 0.56 (P < 0.01). Conversely, the two trees without epicormic shoots exhibited no significant changes in conduit size. Our findings indicate that conduit size at the stem base is determined by hydraulic path length, rather than by cambial age. This suggests that newly formed leaves regulate the vascular conduits supplying them, leading to a hydraulic network structured by multiple, axially sectored pathways.

High-resolution carbon isotope ratio (δ13C) measurements of tree rings have the potential to provide seasonal environmental information. However, due to the complexity of the wood formation processes, the reliability of this method for intra-seasonal reconstruction of growing conditions remains unclear. We therefore investigated the intra-annual variation of δ13C in tree rings of three conifer species (Pinus sylvestris L., Picea abies (L.) H. Karst., Abies alba Mill.) across sites from the Swiss Alps to assess their response to seasonal variation of soil water potential (SWP) and vapour pressure deficit (VPD). Intra-annual δ13C values at a resolution of 10 points per year were assessed using laser-ablation isotope-ratio mass spectrometry. Seasonal δ13C patterns were analysed for synchronicity across trees and species, and their correlation with on-site environmental variables was used to determine the driving factors of δ13C, to reconstruct growing-season dynamics, and to estimate the timings of the growth dynamics and the allocation of carbon to xylem formation. The δ13C patterns showed high synchronicity between species, with characteristic maxima in wet and dry years occurring in the middle of the ring and at the end of the ring, respectively. Seasonal δ13C variations reliably reflected atmospheric dryness. Higher than normal soil dryness hindered the integration of further fresh assimilates into the xylem, thus allowing the identification of species- and site-specific threshold conditions that disrupt wood formation. The δ13C of Scots pine shows the strongest correlations with VPD and SWP, making it an excellent indicator of environmental variability. Silver fir appeared to integrate carbon into xylem structural material over a longer season than the other conifers, whilst Norway spruce shows more plastic, site-specific responses to environmental conditions. In conclusion, we identify how atmospheric and soil drought jointly impact tree growth and intra-annual δ13C patterns across conifer species, offering valuable insights for climate reconstructions and wider applications in forest dynamics.

We investigated the plant-soil linkages of Copaifera langsdorffii Desf., a widely distributed species in the Neotropics, and how the serpentine syndrome leads to dwarfism by comparing soil microbes, soil properties and tree functional traits in serpentine and non-serpentine soils. For this study, we evaluated the presence of heavy metals in the soils and how they affect plant functional traits; differences in the C:N ratio between serpentine and non-serpentine sites as well as soil microbiome by using phospholipid fatty acid technique approach to assess microbial functional groups. We further explored the relations between soil microbes (by using phospholipid fatty acid, i.e., components of cell membranes in microbes used as an indicator of microbial biomass), soil properties, vegetation attributes, leaf nutrients and leaf functional traits. We found a correlation between soil Gram-positive bacteria and iron in the plant leaves; the C:N ratios are higher in serpentine sites, but the two areas are similar to the non-serpentine area; there was no difference between the soil microbes in our study areas, and finally, there is a tendency to dwarfism and xeromorphism in the functional traits of C. langsdorffii in serpentine soils. We found that even though there are differences when comparing C. langsdorffii plants in serpentine and non-serpentine sites regarding the functional traits analysed in our study, the only soil microbe that seems to be interacting with the heavy metals is the Gram-positive bacteria, possibly due to chelating mechanisms.

Water uptake depth is often coordinated with leaf morphology, nutrient and water-use traits across dryland plant species, but such trait coordination remains largely unexplored in plants from more humid but nutrient-poor habitats. We assessed how the year-round water uptake pattern influences the leaf economics spectrum (LES) and isotopic water-use traits across five representative native tree species inhabiting limestone soils and sandstone-derived yellow soils in humid subtropical SW China. We used xylem water isotopes (δ18O, δ2H) to infer water uptake depth; leaf δ13C and Δ18O as proxies for time-integrated water-use efficiency and stomatal conductance, respectively; and key LES traits (specific leaf area, Nmass and Narea) as indices of carbon-nutrient economy. Soil water uptake depth strongly influenced the inter-specific variations in leaf economic and water-use traits, especially during the dry winter-spring period. Shallow-rooted species using water stored in fertile topsoil layers exhibited lower carbon investment per leaf area, higher leaf N and water contents, and higher δ13C values. Conversely, deep-rooted species using deeper soil/bedrock water exhibited thicker and more sclerophyllous leaves combined with lower leaf N, water contents and δ13C values. Across species, leaf δ13C increased with N content, revealing that N-induced differences in photosynthetic capacity are the dominant control over interspecific variation in intrinsic water-use efficiency. Shallow-rooted species exhibited lower foliar Δ18O values (indicative of looser stomatal regulation and water-spender strategy), potentially facilitating nutrient uptake from fertile topsoil. Specifically, Zanthoxylum bungeanum played a central role in shaping the broad water-spender-to-water-saver continuum observed across the target species. Our findings highlight how shallow-rooted tree species can adopt a resource-acquisitive strategy through coupled enhancement of soil water and nutrient capture, stomatal conductance, photosynthetic capacity and water-use efficiency. We provide novel insights into key ecophysiological mechanisms that may help maintain tree species diversity and coexistence in humid but nutrient-poor subtropical habitats.

Cadmium (Cd) contamination has pronounced negative effects on plant physiological processes, while phosphorus (P) as an essential macronutrient might mitigate Cd toxicity by modulating plant adaptivity. This study employed Salix caprea as a model to assess the effects of P on physiological and anatomical characteristics under Cd stress. The results demonstrated that plant growth, e.g., height, basal diameter and biomass, photosynthetic pigment content and net photosynthetic rate were all significantly inhibited by Cd stress. However, adequate P could alleviate these inhibitory effects in contrast to the P deficiency treatment under Cd stress. Phosphorus sufficiency significantly reduced the levels of reactive oxygen species (O₂˙- and H₂O₂) and malondialdehyde (MDA) in roots under Cd stress, while enhancing the activities of antioxidant enzymes such as superoxide dismutase and ascorbate peroxidase, and increasing the contents of non-enzymatic antioxidants, including ascorbic acid and glutathione. These findings indicate that P reduces Cd-induced oxidative damage by adjusting the antioxidant defense system. Furthermore, P sufficiency enhanced the accumulation of phytochelatins and non-protein thiols in roots, thereby promoting complexation and sequestration of Cd into vacuoles. Adequate P enhanced root mineral uptake, which resulted in higher concentrations of magnesium and manganese in roots. Anatomical analysis revealed that P sufficiency significantly increased the stele-to-root area ratio, thereby enhancing transport efficiency and promoting Cd accumulation in aboveground tissues. Moreover, adequate P significantly increased the levels of abscisic acid, indole-3-acetic acid and gibberellic acid under Cd stress, suggesting a mediated role of hormones in the improved tolerance capacity to Cd by P. In summary, P sufficiency conditions enhanced Cd tolerance in S. caprea by coordinating antioxidant defense, metal chelation, root development and hormonal regulation.

Pine wilt disease, instigated by the Bursaphelenchus xylophilus (also called pine wood nematode [PWN]), poses a significant threat to coniferous forests across the globe, leading to widespread tree mortality and ecological disruption. While Japanese larch (Larix kaempferi) is a natural host of PWN, the molecular basis of its responses remains poorly understood. Here, we developed a callus-based parenchymal sentinel (CaPS) system mimicking xylem parenchyma-nematode interactions to bypass multi-tissue interference in traditional sapling studies. After 5 days of PWN inoculation, nematode proliferated 2.85-fold, while the callus exhibited water-soaked lesions and reduced cell viability, indicating a rapid defense activation. (i) Transcriptome analysis revealed 8515 differentially expressed genes related to chitinase signaling, calcium-regulated immunity and antimicrobial compound synthesis. (ii) Metabolomic analysis identified 389 defense-related metabolites (e.g., alkaloids). (iii) Integration of omics data uncovered 71 coordinated pathways categorized into eight functional groups, including reactive oxygen species burst and mitogen-activated protein kinase, and they formed a multi-layered defense network. Importantly, this CaPS system enabled 5-day phenotyping cycles of transgenic callus, significantly accelerating evaluation compared with traditional sapling methods. Our work reveals early-stage conifer immunity against PWN and establishes an accelerated evaluation program for future screening of transgenic callus and breeding resistant larch varieties.

Secondary forests (SFs), which dominate tropical regions and account for more than half of the total forest area, play a crucial role as carbon sinks and contribute significantly to climate change mitigation. However, our understanding of how species respond to ongoing climate change in these forests remains limited, particularly because species performance may shift across successional stages in response to changing environmental filters. Therefore, understanding the factors that influence species regeneration and drought tolerance is essential for predicting their resilience in the face of intensifying climate change. In this study, we evaluated intraspecific variation in hydraulic and anatomical traits of three abundant tree species (Eschweilera coriacea, Licania kunthiana and Tapirira guianensis) occurring in a successional gradient of SFs in the Eastern Amazon and their relationships with soil characteristics. We identified intraspecific variation both among individuals within the same plot and across different plots; however, we did not observe a consistent pattern of trait variation along the successional gradient. In some cases, successional age was associated with variation in anatomical and hydraulic traits, but these relationships were not consistent across species. In addition, soil properties were a key determinant of intraspecific variation. Our findings highlight the complexity of intraspecific trait responses in SFs and underscore the need to consider both species-specific strategies and environmental drivers when predicting forest resilience under future climate change.

Foliar water uptake (FWU) capacity of more anisohydric species is significantly higher than that of relatively isohydric species, yet the underlying mechanisms remain unclear. While leaf nutrient elements may modulate the FWU process, this relationship remains understudied. In this study, we investigated four typical species from the arid region of northwest China and measured their FWU parameters along with various associated traits. The results showed obvious differences in FWU capacity and traits along the isohydric-anisohydric continuum, with more anisohydric species exhibiting higher FWU capacity. Structural equation modeling revealed that leaf water storage structures were the primary factor contributing to the high FWU capacity in more anisohydric species (total effect = 0.25), followed by epidermal traits (total effect = 0.18). Leaf phosphorus affected FWU indirectly via leaf water storage structures (standardized path coefficient = 0.35). This study reveals key drivers and mechanisms underlying the FWU capacity of more anisohydric species, providing a theoretical framework for plant water-use strategies in arid environments. It also helps to predict the water adaptation strategies of different plant functional types under future climate change scenarios.

Leaf nutrient resorption represents a vital nutrient conservation strategy for plants. While trace element resorption patterns have been extensively studied in upland terrestrial plants, they remain poorly characterized in mangrove ecosystems. This study investigated the nutrient resorption efficiency (NuRE) of seven trace elements-iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), sodium (Na) and aluminum (Al)-in mangroves, comparing them with upland terrestrial plants and evaluating their ecological implications under seasonally dry and wet conditions. Field sampling was conducted in Dongzhaigang National Nature Reserve, China, across dry and wet seasons, and green and senesced leaves from 10 mangrove species were analyzed. Our findings revealed distinct resorption strategies between mangroves and upland terrestrial plants. Compared with upland terrestrial species, mangroves presented net accumulation (negative NuRE) of Na (-29.06 ± 6.87%), Mn (-72.71 ± 11.79%), B (-77.36 ± 14.49%), Fe (-123.63 ± 17.98%) and Al (-164.91 ± 33.21%), demonstrating significantly lower NuRE values for these elements. In contrast, mangroves presented a greater NuRE for Cu (57.80 ± 3.50%) than their upland terrestrial counterparts did, whereas Zn resorption (17.39 ± 4.00%) did not differ significantly between the two systems. Our analysis revealed that Na resorption patterns exhibited strong seasonal variations across ecological gradients. During dry seasons, Na accumulation (more negative NaRE) was significantly greater in low intertidal zones, tree species and isobilateral leaves (characterized by symmetrical mesophyll organization). In contrast, wet seasons completely reversed these patterns, favoring accumulation in high intertidal zones, shrubs and bifacial leaves (with dorsiventral mesophyll organization). Green-leaf nutrient concentrations emerged as the primary driver of NuRE, outweighing soil nutrient availability across dry and wet seasons. These findings highlight mangroves' unique nutrient conservation strategies and underscore the importance of foliar nutrient status in predicting ecosystem resilience under seasonal hydroclimatic variations.

More frequent and extreme droughts under global climate change pose major threats to plant diversity and ecosystem productivity. Plant growth is constrained by the interplay between hydraulic failure and reduced carbon assimilation; however, how these carbon-water dynamics jointly regulate growth across functional types, particularly under varying drought intensity and duration, remains poorly understood. We conducted a meta-analysis of 249 studies covering 236 species across diverse biomes to examine differences in growth, carbohydrate allocation and hydraulic responses to drought among functional groups (e.g. evergreen vs deciduous, angiosperm vs gymnosperm, adult plants vs seedling, etc.). We also evaluated how carbon-water dynamics mediate plant growth under drought stress. We found that drought stress consistently reduced plant growth, photosynthetic rate, water potentials and the consequent hydraulic conductivity across species. Growth responses were strongly influenced by leaf phenology (evergreen vs deciduous) and drought intensity. Evergreen species showed greater growth resistance to drought than deciduous species, by maintaining photosynthesis and hydraulic function despite faster declines in water potential. Evergreen species exhibited linear reductions in growth, photosynthesis and water potentials with increasing drought intensity, reflecting gradual physiological adjustments indicative of drought resistance. In contrast, deciduous species showed significant limitation of photosynthesis and growth at drought onset. Our findings provide a quantitative framework linking plant traits related to carbohydrates and hydraulic to growth responses under drought. Understanding how drought affects carbon-water strategy based on leaf phenology advances predictive vegetation models of responses to climate extremes, with critical implications for ecosystem management and maintaining species diversity under global change scenarios.